Surfacing material composition



A. s. BURNS 3,081,186

SURFACING MATERIAL COMPOSITION Filed Oct. 21, 1960 March 12, 1963 Fig. 3

INVEN TOR.

ALBERT S. BURNS BY zzwzwwwww Afforny:

United States Patent assaiss sonractuo Mmrnnnm cosrrosrrion Albert 5. Burns, 64m E. 98th as, Nobiesviile, Ind. Filed Get. 21, 1960, 581'. No. 64,165 s claims. (Cl. lilo-235) The present invention relates to an improved paving composition and construction and more particularly to a paving composition and construction capable of preventing or reducing skidding of automobiles and other vehicles.

One of the causes of the present day high automobile accident rate is the susceptibility of pavement to skidding. As a given section of pavement is subjected to wear over the years, the coarse aggregate therein becomes polished and the surface of the pavement becomes very smooth reducing the gripping action of tires on the pavement. Various solutions have been suggested to combat this problem but without complete success. For example, sharp sand embedded in an asphaltic prime coat has been used to prevent skidding with good results. This prime coat method, however, is short lived, may worsen skidding in hot weather, and produces a sandpaper texture resulting in extremely great tire wear.

It has been found that skidding on wet (or dry) pavement, when not produced by poor manual operation of the vehicle or faulty mechanical condition of the vehicle,

always starts from lateral movement of one or more wheels. Thus, it is desirable that a paving composition be provided which is capable of preventing or resisting lateral skidding of automobile wheels. Accordingly, one of the objects of the present invention is to provide a paving composition capable of resisting such lateral skidding.

A further object of the present invention is to provide an improved paving composition capable of resisting skidding without producing excessive tire Wear.

Still another object of the present invention is to provide an improved paving composition which is durable and has long life, and a reasonable amount of resistance to cracking.

Still a further object of the present invention is to provide a paving composition incorporating novel means for strengthening the bond between certain aggregate and the asphalt matrix both forming a part of the composi tion but without hardening and loss of flexibility of the asphalt matrix.

Another object of the invention is to provide an improved paving composition and construction.

Related objects and advantages Will become apparent as the description proceeds.

In accord with the invention, there is provided a paving composition comprising a sharp edged, hard aggregate having a coating of asphalt hardener thereon. The hard aggregate has a soft aggregate mixed therewith and the complete mixture is bound together by an asphalt cement.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

FIG. 1 is a transverse section of a roadway or the like constructed from the paving composition of the present invention and showing the roadway after it has been subjected to a certain amount of wear.

PEG. 2 is a longitudinal section of the roadway of FIG. 1.

PEG. 3 is a section of a piece of hard aggregate forming a part of the paving composition of the present invention.

For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that nolimitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now more particularly to the drawings, my novel paving composition comprises a hard, sharp-edged aggregate 10 such as granite intermixed with a soft aggregate 11 such as limestone, both the hard and soft aggregate having approximately the same size and passing the three-eighths inch square screen but not passing the one-quarter inch square screen with the most preferable size being known as #4 chicken grit. It should be noted that sizes of aggregate as large as one-half inch and as small as one-fourth inch may be used but are not as desirable because of the fact that they tend to produce a pavement surface which is'too smooth. In any event, no matter what the size of the hard aggregate, the soft aggregate should have the same size as nearly as possible.

The coarse aggregate 1% and 11 is bound together by means of a standard asphalt cement 12 having a standard sand therein. In manufacturing the mix of composition of the invention, sand and cement is used in the conventional manner to fill in the voids between the coarse aggregate and to bind the coarse aggregate together. Thus, the sand and asphalt form a matrix with the coarse aggregate lit and 11 as illustrated in FiGS. 1 and 2.

Referring to FIG. 3, one piece of the coarse, sharpedged aggregate is illustrated. the present invention, it is necessary to place a coating of asphalt hardening material 15 upon the hard aggregate. The purpose of this material is to harden the asphalt just adjacent to the hard aggregate in order to fix the hard aggregate in position and to prevent it from being worked out of the asphalt by heavy trall'ic. Thus, the outer coating upon the hard aggregate illustrated in FIG. 3 is an asphalt hardening material.

The inner coating 15 is used when the hard aggregate is granite to prevent the entry of water into the granite which is a well known hydrophilic material. Since asphalt is slightly soluble in water, silicious aggregates such as granite, tend to loosen in the asphalt under the action of trafiic and as a result of thewater within the silicious aggregate. In the present invention, this is overcome by, the coating 16 which is preferably an abietic type of resin or a blend of such resins. This coating 16 acts in the case of granite and similar hydrophilic materials (as' the hard aggregate) to prevent water from passing into the granite thus preventing weakening of the bond between the granite and the asphalt matrix.

Referring again to FIG. 1, it should be restated thatv this figure is a transverse cross-section and thus, the

tire 17 of a vehicle traveling on the pavement 2b is shown in end elevation. As tires such as the tire 17 repeatedly roll across the pavement 2d, the asphalt matrix and the soft limestone on the sides of the granite is removed to a depth of one or two millimeters as illustrated whereby the sharp edges 21 of the granite are exposed. These sharp edges act to prevent lateral skidding of the tire in a direction transverse of the pavement 20.

Referring to FIG. 2, which as mentioned above is a longitudinal section of the pavement, it can be seen that there is very little removal of the asphalt matrix and lime stone in front of the granite at 22 although there is a certain amount of removal of the matrix and limestone from the rear of the granite at 23, the direction of travel of the vehicles being as shown by the arrow 25. Because of the fact that there is very little removal of asphalt in front of the granite, the pavement does not have the 'above mentioned elfect of extremely great tire Wearand instead produces no more wear than the standard type In making the mix of Percent Asphalt cement 6-7 Soft aggregate (limestone) -20 Coated hard aggregate (granite) 15-20 Sand 60-70 Atypical batch of the present invention would be as follows:

lbs.

Asphalt cement I 65 Limestone 187 Coated granite 187 Sand; 561

Total 1,000

Referring more particularly to the hard aggregate forming a part of the present invention, it should be, as mentioned, between one-half to one-fourth inch in size and preferably #4 chicken grit. As mentioned, the preferred hard aggregate is granite. However, any hard aggregate having sharp edges which are renewed when the material is broken is included within the scope of the present invention. As mentioned, the granite is coated with an abietic type of resin or a blend of such resins. Preferably, the resin has a melting point low enough to make possible coating of the granite in the conventional mixer. If necessary, the aggregate may be heated in orderto accomplish such coating within the mixer.

Alternatively, the hard aggregate could be coated in the mixer by dissolving the resin in a suitable solvent such as dipentene or butyl alcohol or a mixture of solvents and then by adding the solution to the granite while in the mixer in an amount sufiicient to thoroughly wet the granite.

To further specify the amounts of material used in producing the above mentioned typical batch of material, 7.48 pounds ofabietic resin is added to the mixer, the granite aggregate having been previously heated to 325 degrees Fahrenheit. Alternatively, when the above mentioned solvent method is used for coating the granite with abietic resin, 7 .48 pounds of resin dissolved in 1.87 gallons of solvent is added to the granite ofthe above typical batch for the coating of the granite.

After placing the coating 16 upon the hard aggregate, it is then necessary to place the coating 15 thereon. As mentioned above, this coating comprises an asphalt hardening agent. This agent may be either chemical or physical in its action. For example, this material may be a natural asphaltite or a very low penetration asphalt, both of which materials would act to physically harden the asphalt adjacent thereto. As a further example, the asphalt hardener could be a chemical oxidizer such as the oxides of iron or lead. Referring again to the above typical batch, 3.74 pounds of natural asphaltite is added to the. resin coated granite in the mixer in order to provide the coating 15. It should be noted, however, that since thislatter coating action is a thin film reaction, only a very small amount of asphalt hardeneris needed and this amount might be determined by visually noting the color of the batch and adding only a sufficient amount of asphalt hardener to color the batch.

A further alternative embodiment of the invention might include the coating of the granite by an asphalt cement having an epoxy product therein. Such asphalt cements might be used to coat the granite in the mixer. Because of the fact that these cements are sufficiently soluble in asphalt cement to bond securely to the matrix and to provide a waterproof surface bond on the granite, the use of such an epoxy carrying asphalt cement will replace the resin coating and the asphalt hardening coating explained above.

After the hard aggregate has been coated in the mixer as above described, the soft coarse aggregate, sand and asphalt cement are added to the coated aggregate and the materials are mixed conventionally.

As mentioned, the preferred soft aggregate is limestone. However, other materials having similar properties also fall within the scope of the present invention. The size of the soft aggregate should be as nearly that of the hard aggregate as possible and the soft aggregate should not be chalky and should meet A.S.T.M. specifications. Furthermore, the dust content should not be greater than 5%. It should be noted that the limestone also acts to lock the granite in place andto prevent it from working out and loosening.

The sand used in the present invention need meet no particular requirement other than that it is well graded and that 95% thereof will pass the'#4 screen.

The asphalt cement used in the present invention as a binder may be any standard commercially available asphalt cement having a ductility of not less than approximately 30 centimeters and a penetration of approximately 50 to when tested according to the conventional A.S.T.M. method.

In using this material as a surface treatment upon an already constructed pavement, the paving composition should be applied to a thickness of three-fourths of an inch and the surface of the pavement should be cleaned and asphalt primed prior to the application of the composition. All dust should be removed from the pavement prior to coating and the cleaning should be thorough. The primer used should be preferably an RC #1 or #2. The paving composition of the present invention can also be used in new construction as the wearing course on an asphaltic binder.

The paving composition of the present invention has a number of uses. For example, it might be used on airport runways to avoid excessive lateral slide and to assist in the control of the airplane. Further, it might be used as the surface material for curves on roadways and especially those curves having a noticeable bank grade. Also, the composition would be of value on twisting roads and conceivably on the ascending and descending grades of hills.

From the above description, it can be seen that the present invention provides an improved paving composition, capable of resisting skidding without producing excessive tire wear. It can also be appreciated that the present invention provides an improved paving composition which is durable and has long life and is flexible even though the hard aggregate is firmly bonded therein. With regard to the latter point, it will be noted that the asphalt hardener coating 15 on the hard aggregate will act only just adjacent to the hard aggregate to harden the asphalt but will not harden all of the asphalt and thus reduce the flexibility thereof.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention and the scope of the claims are also desired to be protected.

The terminology consisting essentially of when used in the claims is intended to render a particular claim open for the inclusion of unspecified ingredients which do not materially affect the basic and novel characteristics of the composition.

The invention claimed is:

1. A composition consisting essentially of approximately -20 parts by weight of a sharp-edged hard aggregate coated with a binder hardener, approximately 15-20 parts by weight of a soft aggregate mixed with said hard aggregate, approximately 60-70 parts by weight of fine aggregate mixed with said hard and soft aggregates and approximately 6-7 parts by Weight of a bituminous binder holding sai-d aggregates together.

2. A composition consisting essentially of approximate- 1y 15-20 parts by weight of a sharp-edged hard aggregate coated with a binder hardener, approximately 15-20 parts by weight of a soft aggregate; approximately 60-70 parts by weight of sand, said sand, soft aggregate and hard aggregate being mixed together; and approximately 6-7 parts by weight of a bituminous binder holding said sand and aggregates together.

3. A composition consisting essentially of approximately 15 to percent by weight of #4 chicken-grit-sized coated granite aggregate, said granite aggregate having an inner coating of abietic resin and an outer coating of an asphalt hardener, approximately 15 to 20 percent by weight of #4 chicken-grit-sized limestone aggregate mixed with said granite aggregate, approximately 60 to 70 percent by weight of sand, 95 percent by weight of which passes the #4 screen, said sand being mixed with said granite and limestone aggregates, and approximately 6 to 7 percent by weight of asphalt cement binding the mixture together.

4. A paving construction comprising approximately 15-20 parts by weight of sharp-edged, hard, coarse aggregate, approximately 15-20 parts by weight of a soft, coarse aggregate mixed with said hard aggregate, approximately 60-70 parts by weight of fine aggregate mixed with said coarse aggregates, and approximately 6-7 parts by weight of a bituminous binder providing a matrix for said aggregates, said mixture being formed in the shape of a roadway and providing a wearing surface, said hard, sharp-edged aggregate projecting beyond said sand, matrix and soft aggregate at said wearing surf-ace.

5. A paving construction comprising approximately 15-20 parts by weight of sharp-edged, hard, coarse aggregate, approximately 15-20 parts by weight of a soft,

coarse aggregate mixed with said hard aggregate, approximately -70 parts by weight of tine aggregate mixed with said coarse aggregates, and approximately 6-7 parts by weight of a bituminous binder providing a matrix for said aggregates, said mixture being formed in the shape of a roadway and providing a wearing surface, said sand, matrix and soft aggregate being worn away at said wearing surface from the sides of said hard aggregate which face laterally of said roadway and being worn away to a lesser extent from the sides of said hard aggregate which face in the direction of traffic on said roadway.

6. A composition consisting essentially of approximately 15 to 20 percent by weight of hard, sharp-edged coated granite aggregate, said granite aggregate passing the threeeighths inch square screen but not passing the one-fourth inch square screen, the coating of said granite being of asphalt hardening material and waterproofing material other than asphalt, approximately 15 to 20 percent by weight of limestone aggregate of the same size as said graphite aggregate, approximately 60 to percent by weight of sand, percent by weight of which passes the #4 screen, said sand being mixed with said granite and limestone-aggregates, and approximately 6 to 7 percent by weight of asphalt cement binding the mixture together.

7. The composition of claim 6 in which said coating is of abietic resin and asphaltite.

S. A composition comprising approximately 18.7 percent by weight of hard, sharp-edged, coated granite aggregate, said granite aggregate passing the three-eighths inch square screen but not passing the one-fourth inch square screen, the coating of sa-id granite being inwardly of abietic resin and outwardly of asphaltite, approximately 18.7 percent by weight of limestone aggregate of the same size as said granite aggregate, approximately 56.1 percent by weight of sand, 95 percent by weight of which passes the #4 screen, said sand, said granite and limestone aggregates being mixed together and approximately 6.5 percent by weight of asphalt cement binding the mixture together.

References Cited in the file of this patent UNITED STATES PATENTS 2,427,488 Anderson et a1. Sept. 16, 1947 

1. A COMPOSITION CONSISTING ESSENTIALLY OF APPROXIMATELY 15-20 PARTS BY WEIGHT OF A SHARP-EDGED HARD AGGREGATE COATED WITH A BINDER HARDENER, APPROXIMATELY 15-20 PARTS BY WEIGHT OF A SOFT AGGREGATE MIXED WITH SAID HARD AGGREGATE, APPROXIMATELY 60-70 PARTS BY WEIGHT OF FINE AGGREGATE MIXED WITH SAID HARD AND SOFT AGGREGATES AND APPROXIMATELY 6-7 PARTS BY WEIGHT OF A BITUMINOUS BINDER HOLDING SAID AGGREGATES TOGETHER. 